1. Field of the Invention
This invention relates, generally, to endovascular surgical tools. More particularly, it relates to a tool used in balloon angioplasty and stenting of blood vessel narrowings (stenoses).
2. Description of the Prior Art
Percutaneous angioplasty is an efficacious treatment for improving the blood carrying capacity of an artery that has become occluded by plaque, calcification, and other deposits. There are several ways of performing the procedure and the type and number of catheters and other tools used may vary between differing procedures. Typically, a needle puncture is made into an artery and an elongate guide wire is fed through the puncture site until it has traversed the stenotic lesion (the are where the plaque has built up). A guide catheter having a relatively large diameter is then introduced into the artery, using the guide wire to guide it. A balloon-carrying catheter is then fed through the guide catheter, also using the guide wire as a guide. The guide catheter is then advanced to a preselected point so that its distal end is downstream of the stenotic lesion, and the balloon catheter is positioned so that the balloon is in registration with said lesion, also known as a stenosis. The guide catheter is withdrawn a relatively short distance to expose the balloon catheter. The balloon is then inflated to permanently dilate and tear the two inner layers of the artery, thereby enlarging its diameter, breaking up the stenosis, thereby increasing the blood-carrying capacity of the artery. An expandable stent may be carried on the outer surface of the balloon and left in place after the balloon is deflated and withdrawn. Alternatively, a self-expanding stent may be deployed over the treated lesion using a different delivery catheter. The stent holds the arterial walls in their expanded condition. After the balloon is deflated, the balloon catheter is withdrawn into the guide catheter, and both of said catheters and the guide wire are withdrawn to conclude the procedure.
The primary drawback to balloon angioplasty or stenting is the creation of debris and thrombus that can clog blood vessels downstream of the treatment site. The stretching of the two inner arterial walls breaks up the stenotic lesion and creates debris known as emboli. Accordingly, when the balloon is deflated, the emboli flow downstream with the blood. If the stenotic lesion is in the iliac or femoral arteries, the emboli may flow to the feet; this may or may not be problematic. However, if the stenotic lesion is in the carotid artery, the emboli can flow into various brain vessels and cause permanent brain damage. Similarly, kidney damage can ensue from dilating a lesion in the main renal artery. For this reason, balloon angioplasty carries a high risk of embolic complications for stenotic lesions in the carotid, renal, and coronary arteries unless means are provided for preventing the flow of emboli to the blood vessels of the brain, kidney, or heart, respectively.
U.S. Pat. No. 5,833,644 discloses a complex catheter system that deploys at least two additional balloons that flank the main balloon that stretches the blood vessel. When inflated, the auxiliary balloons isolate the treatment area so that emboli cannot flow therefrom. However, no blood can flow to the brain when the auxiliary balloons are inflated, so the physician must perform the treatment in an expedited manner to avoid brain damage arising from oxygen deprivation. This can result in less than optimal treatment. Catheters of this type also include dedicated lumens for aspiration and irrigation and may require a complex electromechanical system to operate and control the saline flow rate, pressure, and the like.
PCT patent application No. PCT/US98/01894 filed by Yadav, published Aug. 6, 1998, discloses an emboli-catching device that is mounted to the distal end of a guidewire. It is positioned downstream of the stenotic lesion and opened up, much like an umbrella, to catch the emboli created by inflation of the angioplasty balloon. It is designed for use in the carotid artery and is formed of a material that is permeable to red blood cells so the brain is not deprived of oxygen during its deployment. However, since it must be positioned downstream of the stenotic lesion, it cannot be used in the lower half of the body because such use would require that it be fed to its operative location from a point in the upper half of the body. Moreover, the mechanism required to deploy and retract and emboli-catching means requires a dedicated sheath which makes the procedure relatively complex.
Several prior art emboli-catching devices also rely upon mesh-carrying frames that are formed of a flexible and resilient material such as a nickel-titanium alloy. The problem with such devices is that they pop open when they emerge from a containment catheter. Some of them spring open under their inherent bias until they hit the interior walls of an artery, and others spring open to a predetermined diameter that may be less than the diameter of an artery. In either case, the physician cannot instantaneously control the amount of opening or closing of the mesh. In other words, the nickel-titanium devices are either fully open or fully closed and the physician cannot open or close such devices to an infinite plurality of functional positions of adjustment because the opening or closing of the emboli-catching device is not under the positive control of the physician.
What is needed, then, is an emboli containment and removal device that does not block blood flow when in use, which can be used with any diagnosis or treatment catheter, which is small, which is mechanically simple in construction, and which is under the positive control of the physician. Moreover, such a device is needed that can be used in the carotid artery and in other blood vessels, including those in the region of the kidneys, heart, and peripheral blood vessels.
However, it was not obvious to those of ordinary skill in this art how the needed improvements could be provided, in view of the art considered as a whole at the time the present invention was made.